Accurate characterization of prostate cancers is a major problem facing both for managing individual patients and for the selection and monitoring of subjects in clinical trials. This project, now completed its 13th year, is focused on the development and application of 3D MR spectroscopic imaging to address this clinical problem by providing metabolic assessments of the presence and extent of human prostate cancers. This project has been extremely successful, resulting in the technical development of specialized MR methods, improved understanding of metabolite levels in normal and cancerous prostate tissues, and also in supporting the development of clinical prostate MRSI products that are now widely available on commercial 1.5T scanners. Although 1.5T prostate MRSI is now FDA approved and widely used, there is increasing desire from referring physicians, radiologists, prostate cancer research community, and even patients themselves for 3T prostate MRSI with its potential doubling in performance. The development of 3T prostate MRSI has, however, turned out to be a highly complex task and has required a major redesign of virtually all aspects of the acquisition and analysis techniques developed for 1.5T. In this renewal project, we will develop and apply new 3T MRSI methods with the goal of improving the sensitivity and accuracy for characterizing prostate cancer presence and extent. Our preliminary 3T studies have demonstrated challenges in applying this technique at high field, but also have shown major improvements in SNR and spectral resolution that indicate a great potential for significant improvements in accurately measuring prostate cancer extent before and following therapy. While our preliminary 3T MRSI results have shown dramatic improvements in spatial and spectral resolution for prostate cancer characterization, the prototype methods require further development and the benefit of 3T prostate MRSI is yet to be defined. In this project we will develop new specialized 3T prostate MRSI techniques and apply them in patient studies to determine: a) improvements over 1.5T studies, b) sensitivity, specificity and volume accuracy measurements in prostatectomy patients, and the c) ability to detect and monitor hormone therapy response.